Tuesday, May 28, 2013

CO2 Sequestration Technique Yields 'Supergreen' Hydrogen Fuel

The team demonstrated, at a laboratory scale, a system that uses the
acidity normally produced in saline water electrolysis to accelerate
silicate mineral dissolution while producing hydrogen fuel and other
gases. The resulting electrolyte solution was shown to be significantly
elevated in hydroxide concentration that in turn proved strongly
absorptive and retentive of atmospheric CO2.
Further, the researchers suggest that the carbonate and bicarbonate
produced in the process could be used to mitigate ongoing ocean
acidification, similar to how an Alka Seltzer neutralizes excess acid in
the stomach.
"We not only found a way to remove and store carbon dioxide from the atmosphere while producing valuable H2,
we also suggest that we can help save marine ecosystems with this new
technique," says Greg Rau, an LLNL visiting scientist, senior scientist
at UC Santa Cruz and lead author of a paper appearing this week in the Proceedings of the National Academy of Sciences.
When carbon dioxide is released into the atmosphere, a significant
fraction is passively taken up by the ocean forming carbonic acid that
makes the ocean more acidic. This acidification has been shown to be
harmful to many species of marine life, especially corals and shellfish.
By the middle of this century, the globe will likely warm by at least 2
C and the oceans will experience a more than 60 percent increase in
acidity relative to pre-industrial levels. The alkaline solution
generated by the new process could be added to the ocean to help
neutralize this acid and help offset its effects on marine biota.
However, further research is needed, the authors say.
"When powered by renewable electricity and consuming globally
abundant minerals and saline solutions, such systems at scale might
provide a relatively efficient, high-capacity means to consume and store
excess atmospheric CO2 as environmentally beneficial
seawater bicarbonate or carbonate," Rau says. "But the process also
would produce a carbon-negative 'super green' fuel or chemical feedstock
in the form of hydrogen."
Most previously described chemical methods of atmospheric carbon
dioxide capture and storage are costly, using thermal/mechanical
procedures to concentrate molecular CO2 from the air while recycling reagents, a process that is cumbersome, inefficient and expensive.
"Our process avoids most of these issues by not requiring CO2
to be concentrated from air and stored in a molecular form, pointing
the way to more cost-effective, environmentally beneficial, and safer
air CO2 management with added benefits of renewable hydrogen fuel production and ocean alkalinity addition," Rau says.
The team concluded that further research is needed to determine
optimum designs and operating procedures, cost-effectiveness, and the
net environmental impact/benefit of electrochemically mediated air CO2 capture and H2 production using base minerals.